How IR35 status affects the true cost of hiring UK contractors
IR35 status directly determines how a UK contractor engagement gets taxed — and that single decision reshapes costs for everyone in the supply chain.
What "Inside IR35" does to costs
When a role falls inside IR35, the fee-payer must operate PAYE on the contractor's deemed employment income. This triggers two immediate cost consequences. Income Tax and employee NICs are deducted from the contractor's pay, and the fee-payer must also pay employer NICs on top.
Employer NICs currently run at 13.8% on relevant earnings above the secondary threshold, as detailed in this IR35 inside vs outside guide. That percentage applies directly to the gross contract rate, making inside-IR35 engagements materially more expensive unless the headline day rate is renegotiated downward.
For large fee-payers, the Apprenticeship Levy adds another 0.5% on pay bills exceeding £3 million — a marginal but real additional cost layer.
The "same rate" trap contractors fall into
Many contractors make one critical mistake: they accept the same headline rate inside IR35 as they previously earned outside it. This silently transfers the employer NIC burden onto their net income, reducing take-home without changing the invoice amount.
At the same gross day rate, an inside-IR35 contractor loses the flexibility to plan PSC dividends. They also gain no employment rights such as paid leave, pension, or redundancy protection.
How IR35 status affects contractor vs. client costs
Arrangement | Employer NICs | Contractor tax route | Key cost risk |
|---|---|---|---|
Outside IR35 (PSC) | None via fee-payer | Corporation tax + dividends | Contractor bears status risk |
Inside IR35 (PAYE) | Fee-payer pays \~13.8% | PAYE Income Tax + employee NICs | Fee-payer bears payroll cost |
Umbrella company | Funded from assignment rate | PAYE via umbrella | Rate transparency; margin cost |
Who decides and when the rules changes
Public sector clients have held responsibility for IR35 status determinations since April 2017. Medium and large private sector clients took on that same responsibility from 6 April 2021. In both cases, the client must issue a Status Determination Statement (SDS) explaining the decision.
Small private sector clients remain an exception; the contractor's PSC still determines its own status there.
How costs get negotiated in practice
Understanding how IR35 status affects contractor costs helps explain market responses to inside-IR35 determinations. These typically follow one of two paths.
Either the client reduces the assignment rate to offset employer NICs, pushing the cost burden to the contractor. Or scarce-skill roles attract a rate premium to retain talent, raising the client's total cost. Neither outcome is automatic — it depends on bargaining power and role scarcity.
Navigating IR35 without the compliance headache
For clients hiring tech talent, IR35 status management adds real administrative and financial risks (see Proxify's hiring guides for role-specific guidance). Proxify is built to absorb that complexity.
Its contractual framework and compliance guidance help clients navigate IR35 and similar workforce regulations. Hiring decisions stay focused on skill fit, not tax liability.